A truck carrying a tunnel boring cutter-head gets a flat tire.
The driver pulls over and removes the flat tire and is about to replace it with the spare tire when a Corvette drives by really fast and the wind from the speed blows the wheel nuts away and the driver can’t find them anymore.
A little boy on a bicycle rides by and asks the driver why does the truck only have 3 tires on it.
The driver tells the little boy that he can’t put the 4th tire on because he lost the wheel nuts for it.
The little boy looks at him, smiles and says, “you still have them” and then whispers in the driver’s ear.
The driver laughs and manages to put the 4th tire on and drives away.
What did the little boy whisper in the driver’s ear?
Remove a nuts from each of the three wheels and use them to bold on the 4th wheel.